It is of great significance to summarize and sort out the theoretical logic of the grass-roots party building leading the "three governance integration" urban and rural grass-roots governance system in the new era from the theoretical pedigree and historical changes. From the perspective of Du Zanqi's "brokerage mechanism" theory, the historical changes of China's urban and rural grass-roots governance system have gone through several important stages, such as "protective brokerage", "profit-making brokerage", "administrative brokerage", and "resource-based brokerage", while "integrated brokerage" can be seen as the essential characteristics and theoretical logic of the "three governance integration" model led by the grass-roots party building in the new era, Its essence is to bring the "political party" back to the local governance field, and form a governance model with grass-roots party building as the integration, cultivating publicity as the goal, and consultative governance as the main form. Under the role of "integrated brokerage", the "empowerment" of national governance and the "empowerment" of grass-roots organizations are realized through the authority of the party organization, the reconstruction of local public social relations and principal-agent relations is realized, and the rural governance dilemma of the lack of exogenous authority and the decline of endogenous authority is effectively improved.